Various electronic musical instruments have been suggested which output audio data and musical performance information of musical instruments (for example, see Patent Literature 1).
Musical performance information of musical instruments is stored as easily modifiable MIDI data separately from audio data. For this reason, an electronic musical instrument includes an audio terminal and a MIDI terminal, such that audio data is output from the audio terminal and musical performance information of a musical instrument is output from the MIDI terminal. Thus, two terminals (audio terminal and MIDI terminal) have to be provided.
Since MIDI data includes tempo information, it is easy to regulate the reproduction time (tempo). In synchronizing audio data and MIDI data, audio data is recorded in synchronization with MIDI data. When existing audio data is used, it is necessary to manually regulate tempo information of MIDI data so as to match audio data. However, when the tempo is changed in the course of audio data, it takes a lot of labor to manually regulate the tempo information of MIDI data.
Various electronic musical instruments have also been suggested which control an external apparatus (for example, see Patent Literature 1).
For example, when a mixer is controlled by an electronic musical instrument, the electronic musical instrument stores a control signal for controlling the mixer as MIDI data, and outputs MIDI data to the mixer to control the mixer. For this reason, the electronic musical instrument has to include an audio output terminal for outputting an audio signal and a MIDI terminal for outputting MIDI data.
Hence, in the data superimposing method described in Patent Literature 1, digital audio data and musical performance information of a musical instrument are associated with each other and output, such that audio data and musical performance information of a musical instrument are output from a single terminal.
In recent years, a signal processing technique, such as time stretch, has been used so as to regulate the tempo of audio data (see Patent Literature 2).
A technique has been suggested which embeds various kinds of data into an audio signal. For example, Patent Literature 3 describes a technique which embeds data into an audio signal by using an electronic watermark for the purpose of copyright protection.
Patent Literature 4 describes a technique which embeds a control signal into an audio signal in a time-series manner by using an electronic watermark.